1. Field of the Invention
The present invention relates to a composition for inducing or stimulating secretion of insulin-like growth factor-1. More particularly, the present invention relates to a pharmaceutical or a food composition for inducing or stimulating secretion of insulin-like growth factor-1.
2. Description of the Related Art
Insulin-like growth factor (hereinafter referred to as “IGF-1”) consists of single chain polypeptides containing 70 amino acids, which is primarily secreted in liver. IGF-1 exhibits its physiological function by virtue of IGF-1 receptor. Numerous studies have been performed for the physiological function of IGF-1, and as a result, various functions of IGF-1 such as promotion of protein biosynthesis, lowering blood sugar level and facilitation of cell differentiation have been revealed.
For example, it has been reported that IGF-1 is necessary for neural stem cell proliferation and low IGF-1 levels in older women is directly associated with poor muscle strength and mobility. It is demonstrated that administration of IGF-1 is able to regenerate skeletal muscle. In addition, ethanol abuse in alcoholics may lead to decreased IGF-1 bioavailability. IGF-1 is also pivotal in cell proliferation and exhibits treatment effect in diabetic patient (Types 1 and 2) (Thraikill K M, Diabetes Technol Ther., 2(1):69-80(2000)).
It has been revealed that low serum concentrations of IGF-1 are associated with femoral bone loss in a population-based sample of postmenopausal women and IGF-1 is markedly reduced in the acute phase of myocardial infarction. IGF-1 also has been proved to have a protection ability to lesion resulted from ischemiareperfusion in several organ and to prevent neural cells from apoptosis.
As described in Woods K. A. et al., N. Engl. J. Med., 335:1363(1996), patients with IGF-1 deficiency suffers from pre- and postnatal growth failure, mental retardation, microcephaly, and sensorineural deafness and such patients have an inability to produce IGF-1 either locally or systemically while elevated growth hormone secretion combined with an intact growth hormone signaling pathway is observed. Administration of IGF-1 to patients with IGF-1 deficiency is responsible for improvement of body composition, insulin sensitivity, bone mineral density and linear growth (K. A. Woods. et al., J. Clin. Endocri. & Met., 85:1407(2000)).
Furthermore, according to Blum et al. (J. Clin. Endocrinol. Metab. 76:1610-1616(1993)), young man who has a low level of IGF-1 and IGF binding protein 3 (IGFBP-3) usually shows shorter height, and Ranke et al., Horm. Res. 44: 253-264 (1995) discusses that long-term therapy with IGF-1 is very effective in increasing the rate of linear growth. Namely, IGF-1 is very useful in treatment of patients suffering from deficiency of growth hormone.
As described above, IGF-1 represents various physiological function in cooperative manner with growth hormone or independent manner.
U.S. Pat. No. 5,240,961 discloses methods of treating reduced insulin-like growth factor levels and bone loss associated with aging which include administering L-carnitine and/or its precursors thereof. U.S. Pat. No. 5,466,670 discloses a method for treating Type 1 diabetes mellitus by subcutaneously administering to a patient suffering from Type 1 diabetes mellitus, IGF-1 in a dose effective to achieve an IGF-1 serum level of up to 400 ng/ml that is characteristic in healthy individuals.
In addition, U.S. Pat. No. 5,861,373 discloses a method of treating neural damage suffered after a CNS insult affecting glia or other non-cholinergic cells in a mammal, comprising administering to the central nervous system of said mammal a medicament comprising an effective amount of IGP-1 and/or a biologically active analog of IGF-1.
Hitherto, the effective substances or compositions capable of increasing IGF-1 level in body have not been developed.
Therefore, there is a long-felt need to develop substances or compositions for treating patients suffering from IGF-1 deficiency.
Throughout this application, various patents and publications are referenced and citations are provided in parentheses. The disclosure of these patents and publications in their entities are hereby incorporated by references into this application in order to more fully describe the present invention and the state of the art to which this invention pertains.